William: Meaning, origin, and popularity of the boy's name William plus advice on William and other baby names from the bestselling nameberry experts. Meaning, Will + helmet (protection). Region of origin, Northern Europe. Other names. Nickname(s), Will, Willie, Willy. Related names, Wilhelm, Guillermo, Guillaume, Guglielmo, Guilherme, Gwilym. Popularity, see popular names. William is a popular given name of old Germanic origin. It became very popular in the English Meaning : Will + helmet (protection). What is the meaning of William? How popular is the baby name William? Learn about the meaning, origin, and popularity of the name William. FREE William.